1. Field of the Invention
The present invention relates to a projection zoom lens that includes six lens groups and a projection display apparatus using the same.
2. Description of the Related Art
Recently, projection display devices using a transmissive or reflective liquid crystal or projection display devices using a light valve, such as DMD display devices, have been used widely. As projection lenses for use with such projection display devices, projection lenses that use zoom lenses capable of changing the size of a projection image have been used increasing as described, for example, in Japanese Unexamined Patent Publication No. 2004-138640 (Patent Document 1), Japanese Unexamined Patent Publication No. 2006-234893 (Patent Document 2), and Japanese Unexamined Patent Publication No. 2009-020189 (Patent Document 3). Recently, zoom lenses having a high rate of change in the size of a projection image, i.e., having a high zoom ratio have been demanded.
Further, a lens shift function for laterally shifting a projection image and a function for displaying a large image with a short projection distance have become demanded for the projection display devices. In order to respond to such demands, it is necessary to broaden the angle of view of the zoom lens.
Further, for an optical system that uses a plurality of light valves, a space for inserting a luminous flux combining optical system, such as a combining prism or the like, for combining each color luminous flux from each light valve is required, thereby resulting in a long back focus.